The R plasmid genes coding for chloraphenicol and streptomycin resistance in E. coli will be analyzed. A series of in vitro and in vivo mutations will be induced in the promotor regions of the chloraphenicol acetyl transferase gene and assayed for their effects on the level of enzyme activity and m-RNA. The nucleotide-sequence of the streptomycin adenyl transferase gene and promotor will be determined and compared with that of chloramphenicol acetyl transferase. The chloramphenicol resistance transposon, Tn9, consists of the chloramphenicol transacetylase gene bounded by directly repeated ISI sequences. Deletions and rearrangements of Tn9 will be constructed and tested for transposition proficiency. The objective of these experiments is to determine whether the ISI sequences code for a gene required for transposition and whether inversion of the directly repeated ISI sequences affect transposition. The N. crassa catabolic dehydroquinase gene has been cloned and is expressed in E. coli. The nucleotide sequence of this gene and its promotor will be determined. A series of mutations will be induced in dehydroquinase promotor region and tested for their effects on the expression of dehydroquinase in E. coli and N. crassa. Hybrid promotor-structural gene combinations containing the dehydroquinase promotor and chloramphenicol acetyl transferase gene will be constructed and tested for their activity in N. crassa.